Inductive magnetic heads are commonly employed to perform recording and reading of data. The constant demand for high recording density disk drives with smaller physical sizes, higher storage capacities and better performance requires manufacturers to build recording components that are capable of storing data with decreased data track widths and increased linear recording densities. This poses technical problems in the design and manufacture of magnetic transducers.
Magnetoresistive (MR) heads can read information on a record medium with much narrower data track widths and yield improved signal-to-noise ratio. The output signal generated during the data reading process is independent of the traveling speed of the recording medium. A typical MR head includes an MR sensor sandwiched between two magnetic shield layers. Disposed between the MR sensor and the magnetic shield layers are insulating layers. During the data reading mode, the magnetic shields act as magnetic flux guides confining the magnetic flux emanating from a record medium, and allow selected flux to be snsed by the MR sensor. Changes in magnetic flux correspondingly vary the resistivity of the MR sensor. A direct electric current passing through the MR sensor in turn generates a varying voltage which representss the information stored by the record medium.
In practice, miniaturized MR read heads experience various practical problems. For example, the MR layer in the magnetic head needs to be properly biased. The ferromagnetic MR layer at its natural state comprises a multiple number of magnetic domains separated by domain walls. These domain walls are highly unstable. During normal operation, the constant merging and splitting of the domain walls generate undesirable signal noise, commonly called Barkhausen noise, which degrades the performance of the magnetic head. To suppress the signal noise, hard magnetic bias layers are normally attached to the ferromagnetic layer for the purpose of aligning the magnetic domains in a single domain configuration. Furthermore, to position the ferromagnetic layer in the linear operating region, another bias, called the transverse bias needs to be provided to the ferromagnetic layer. A soft adjacent layer formed of a material with relatively high resistivity and minimal MR response is disposed adjacent to and spaced from the ferromagnetic layer to provide the transverse bias.
For the above reasons, there is a need to provide magnetic transducers that can interact with storage media having narrow data tracks with high linear recording densities, yet sufficiently sensitive to sense only the data signals being read from the recorded magnetic medium without the undesirable signal noise.